Asian Cardiovasc Thorac Ann 2000;8:271-274
© 2000 Asia Publishing EXchange Pte Ltd
Aortocaval Fistula Due to Abdominal Aortic Aneurysm Rupture
Mohammed Akbar Bhat, MCh,
Kurur Sankaran Neelakandhan, MCh,
Madathipat Unnikrishnan, MCh,
Vijit Koshy Cherian, MCh,
Sandeep Attawar, MCh,
Ghulam Nabi Lone, MCh
Department of Cardiovascular and Thoracic Surgery
Sree Chitra Tirunal Institute of Medical Sciences and Technology
Thiruvananthapuram, Kerala, India
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For reprint information contact: Mohammed Akbar Bhat, MCh Tel: 91 194 42 7348 Fax: 91 194 42 3470 email: root{at}skims.ren.nic.in Department of Cardiovascular and Thoracic Surgery, Sheri Kashmir Institute of Medical Sciences, Post Bag No. 1061, GPO, Srinagar, Kashmir 190001, India.
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Abstract
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Aortocaval fistula is a rare complication of rupture of an aortic aneurysm into the inferior vena cava. Prompt surgical repair is mandatory for salvage. Emergency surgery was performed in 2 cases of aortocaval fistula. The underlying etiology was polyarteritis nodosa in one patient and atherosclerosis in the other. Polyarteritis nodosa leading to abdominal aortic aneurysm with aortocaval fistula is reported for the first time.
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Introduction
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An abdominal aortic aneurysm (AAA) usually ruptures into the retroperitoneal space but on rare occasions, it can erode into the adjacent inferior vena cava (IVC), leading to aortocaval fistula. Spontaneous rupture of an AAA into the adjacent vena cava occurs in less than 1% of all aneurysms and in approximately 3% of ruptured aortic aneurysms.
1
,
2
Factors influencing the clinical manifestations include the origin, size, location, and duration of the fistula. Aortocaval fistula may present atypically, leading to delay in diagnosis and management.
1
,
3
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Case Reports
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Case 1
A 38-year-old man presented with low backache and hemorrhagic shock. He had tachycardia (pulse, 160 beats•min
–1
), systemic blood pressure of 80 mm Hg, and central venous pressure of 18 mm Hg. A vague peri-umbilical mass with a thrill was palpable. The patient had biventricular failure. He was anemic (hemoglobin, 90 g•L
–1
) with a raised erythrocyte sedimentation rate (52 mm•h
–1
) and he tested positive for hepatitis B surface antigen. However, renal function was normal (blood urea nitrogen, 160 mg•L
–1
; serum creatinine, 8 mg•L
–1
). Vascular Doppler ultrasonography and contrast computed tomography (CT) of the abdomen confirmed a fistula between the infrarenal abdominal aorta and the IVC. The patient underwent emergency exploration on inotropic support. Using a midline transperitoneal approach, an infrarenal AAA (6 x 8 cm) with a small retroperitoneal hematoma was found. The superior and inferior mesenteric arteries had a beaded appearance due to small aneurysms at their branch points, but there was no such finding in the branches of the celiac axis. After achieving control of the aorta proximally and the iliac arteries distally, the IVC and common iliac veins were occluded by digital compression. The aneurysm was opened directly and a fistulous opening (4 x 4 mm) was visualized at the right lateral aspect of the lower part of the abdominal aorta, just proximal to its bifurcation (
Figure
1
). Two Fogarty catheters (6F) were introduced through the fistulous opening into the IVC, one upstream and one downstream to the blood flow, thereby achieving endoluminal control of the IVC. The fistula was closed directly with interrupted Teflon-pledgeted 3/0 polypropylene sutures. A Dacron aortoiliac bifurcation graft (16/8 mm) was anastomosed to the aorta proximally and the common iliac arteries distally. Histopathology of the biopsy from the aneurysmal wall revealed polyarteritis nodosa. Postoperatively, the patient had a smooth recovery and was discharged on the 12th postoperative day. He has been managed as a case of polyarteritis nodosa for the last 2.5 years and has been complication-free since the operation.
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Figure 1.
Operative photograph showing the opened aortic aneurysm in case 1. The aortocaval fistula was visualized through the lumen of the aorta.
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Case 2
A 52-year-old diabetic male presented with dysuria and swelling of both lower limbs over a period of 2 weeks. He was found to have a pulsatile periumbilical mass with a thrill. His blood pressure was 120/80 mm Hg in the upper and lower limbs. Renal function was impaired (blood urea nitrogen, 420 mg•L
–1
; serum creatinine, 17 mg•L
–1
; and creatinine clearance, 28.9 mL•min
–1
). Ultrasonography of the abdomen revealed an AAA and IVC occlusion with thrombus. Although contrast CT showed a leaking AAA with iliac vein thrombosis, it did not detect an aortocaval fistula. However, aortography confirmed a leaking AAA with aortocaval fistula (
Figure
2
). A midline laparotomy was performed. There was an infrarenal AAA proximal to the bifurcation of the aorta. The IVC was pulsating like an artery. The aorta and both common iliac arteries were clamped. The common iliac veins and IVC were controlled with finger pressure. The aneurysm was incised to the right of the aorta. Clots were evacuated and the aortocaval fistula (6 x 4 mm) was identified on the right posterolateral aspect of the aorta. The fistula was closed with interrupted Teflon-pledgeted 3/0 polypropylene sutures. The aorta was repaired with a 16/8-mm Dacron graft (
Figure
3
). Histopathology of the biopsy from the aneurysmal wall was consistent with a diagnosis of atherosclerosis. Culture of the atheroma-tous material and clots revealed coagulase-negative staphylococci. Renal parameters reverted to normal on the 3rd postoperative day. During follow-up of 2 years, the patient had no signs of cardiac or renal failure nor arteriovenous insufficiency in the legs (
Figure
4
).
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Figure 2.
Aortogram (digital subtraction angiogram) showing the abdominal aortic aneurysm with aortocaval fistula in case 2.
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Figure 3.
The repaired aorta with the Dacron bifurcation graft after closing the aortocaval fistula in case 2.
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Discussion
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Most cases of aortic rupture are due to arteriosclerotic aneurysms, but syphilitic and mycotic aneurysms, Marfan's syndrome, Ehlers-Danlos syndrome, Takayasu's arteritis, and penetrating injury such as stab or gun shot wounds are additional causes.
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,
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Iatrogenic injury leading to aortocaval fistula has been reported in lumber disc surgery. However, aortocaval fistula as a complication of polyarteritis nodosa has not been reported previously. Polyarteritis nodosa is a form of necrotizing arteritis that typically involves medium-sized arteries but may occa-sionally involve large arteries. Fever, raised erythrocyte sedimentation rate, eosinophilia, and hepatitis B surface antigen are often present.
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Case l had a raised erythrocyte sedimentation rate and a positive finding of hepatitis B surface antigen, but no fever or eosinophilia. Although this patient had aortocaval fistula and involvement of the mesenteric arteries, his kidneys and heart were spared.
High-output cardiac failure due to increased venous return is responsible for most of the clinical manifestations of aortocaval fistula. Bilateral pedal edema is caused by venous hypertension in the lower half of the body, which may lead to hematuria in 17% to 24% of patients.
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Renal insufficiency, as seen in case 2, is caused by markedly elevated renal venous pressure and decreased mean arterial pressure, leading to reduced renal blood flow. Retro-peritoneal and intraperitoneal rupture of AAAs have different clinical presentations compared with rupture of an AAA into the IVC.
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Aortography is the definitive diagnostic modality for confirmation of aortocaval fistula. However, color-coded duplex scanning, dynamic CT scanning, and magnetic resonance imaging are noninvasive and fairly accurate for diagnosis of aortocaval fistula.
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In case 2, the diagnosis was missed by ultrasonography that revealed AAA and IVC occlusion with thrombus. CT also missed the diagnosis and indicated only a leaking AAA with iliac vein thrombosis, although there was no thrombus in the IVC or iliac veins and the patient had an aortocaval fistula. Therefore, aortography should be performed in all cases where there is clinical suspicion of aortocaval fistula.
Urgent surgical exploration is the only way to salvage such patients. The aneurysm should be minimally manipulated before achieving control of the aorta and IVC proximal and distal to the aneurysm and fistula, to prevent paradoxical embolization of intraluminal clots and atheromatous material.
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A Swan-Ganz catheter is essential during surgical repair since large fluxes in fluid load to the heart must be carefully monitored. While the aortocaval fistula is being repaired, increased cardiac afterload from aortic clamping and reduced preload due to IVC occlusion impose a high risk of cardiac decom-pensation.
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The situation is reversed when the aortic clamps are removed and this needs delicate management by the anesthesiologist. The reported operative mortality of spontaneous aortocaval fistula caused by rupture of an AAA ranges from 20% to 55%.
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Most of the reported deaths were due to misdiagnosis or delay in diagnosis.
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Several factors may contribute to misdiagnosis. In some patients with aneurysmal disease, mural thrombus within the aneurysmal sac may partially or totally obstruct the fistula and obscure the typical continuous bruit.
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More common, however, is failure to examine the abdomen for a bruit.
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The key to diagnosis is suspicion of the com-plication in every case of AAA likely to have ruptured.
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Good clinical acumen coupled with timely surgical intervention should salvage all cases of aortocaval fistula.
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Abstract
Introduction
